Why is it important that ligands and cell receptors have a specific shapes? what would happen if all ligands and receptors have the same shape?

'which of these statements about the scientific method is not true? all experiments must follow the same number of steps in the procedure. experiments may be repeated several times. some unexpected results can be beneficial. experimental results may or may not support the hypothesis.

When a person is exercising the body needs to deliver increased amounts of oxygen to the muscles which component of blood ensures that the muscles will receive it

Which direction does the energy flow in this energy pyramid ?